Alarm signal channel control circuit for burglar and fire alarm system

ABSTRACT

A control circuit which, in one state, appropriate for the day season, inhibits an alarm signal channel and furnishes a signal indicative of such &#39;&#39;&#39;&#39;day&#39;&#39;&#39;&#39; state. The control circuit responds to collective command and circuit-closing and safe sensor-stateindicating operations to assume another condition in which it enables the alarm signal channel and sends out a signal indicative of the other or night-season state and enables lamp circuitry that verifies the collective existence of such other state and such safe sensor-state indication.

United States Patent [191 Cook [111 3,831,164 Aug. 20, 1974 ALARM SIGNAL CHANNEL CONTROL CIRCUIT FOR BURGLAR AND FIRE ALARM SYSTEM Inventor: Charles W. Cook, Huntsville, Ala. Assignee: Avco Corporation, Huntsville, Ala. Filed: Apr. 27, 1973 Appl. N0.: 355,030

US. Cl. 340/276, 340/214, 340/227 R, 340/420 Int. Cl. G08b 19/00, 60% 29/00 Field of Search 340/276, 214, 420, 227 R References Cited UNITED STATES PATENTS 75 6/1953 Roe et al. 340/276 SENSORS v v /i i TRANSMiTCfZjC 953% RING BACK SIGNAL FROM TRANSPONDER Primary Examiner-Glen R. Swann, Ill

57 ABSTRACT I A control circuit which, in one state, appropriate for the day season, inhibits an alarm signal channel and furnishes a signal indicative of such day" state. The

control circuit responds to collective command and 5 Claims, 1 Drawing Figure ALARM TO TRANSPONDER DAY OR NIGHT 'SlGNAL TO TRANSPONDER Pmzmwwszww I 333L164 SENSORS lo ALARM TO TRANSPONDER 52 TRANSMIT 5 0 CLOSE VERIFY +v 53 25 55 DAY OR NIGHT i j I SIGNAL 56 l6 1 IT TO TRANSPONDER 5T I4 26 I5 29 I3 I RING BACK 4' l8 4.) SIGNAL FROM TRANSPONDER I9 M DAY 0 T ALARM SIGNAL CHANNEL CONTROL CIRCUIT F OR BURGLAR AND FIRE ALARM SYSTEM BACKGROUND OF THE INVENTION The present invention is of particular utility in burglar and fire alarm systems of the type which comprise a central station and a plurality of monitor-transponder pairs, one pair being located at each customer location.

The primary object of the present invention is to provide means to assure that a safe condition is indicated by the various fire and burglary sensing devices before the alarm signal channel is effectively coupled to the local monitor or to a central monitor.

Another object of the invention is to provide means for preventing effective connections between the sensing devices and the output of the alarm signal channel unless all of the following three conditions are fulfilled: (1) a day-night switch is in the night position; (2) the sensors are safe; and (3) a close switch is closed.

Another object of the invention is to provide a single shot delay circuit that permits an operator to leave the customer location, to open the door instantaneously and to permit the door to close, without an alarm being transmitted to the monitor.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of the invention, together with other and further objects, advantages and capabilities thereof, reference is made to the single FIGURE of the drawings which is a circuit schematic of an improved alarm channel control circuit in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the invention there is provided a control circuit of flip-flop 11. In the set state, appropriate for the day season, as when switch 22 is closed on contact 19, this flip-flop inhibits conductivity of transistor 33 which is in the alarm signal channel. Additionally, the control circuit causes to be furnished, over line 29, a signal indicative of the day stateThe flip-flop 11 responds to collective command (by closing switch 22 on contact 21) and circuit closing (at 24) and safe sensor state indicating (by positive voltage on line 23) operations to assume another condition (reset) in which it enables the alarm signal channel (at 33) and sends out (on line 29) a signal indicative of the other or night season state and enables lamp circuitry (52, 53 and 54, 55) that verifies the existence of such other state and such safe sensor state indication.

As indicated above, the major control functions are performed by a flip-flop 11 comprising a pair of NPN transistors 12 and 13. The emitters of these transistors are grounded. The collector-to-base feedback connections are provided by resistors 14 and 15. Collector load resistors 16 and 17 are connected to a suitable source of bias current (not shown).

The day-night switch 22 provides an inhibiting circuit which is optionally selected. That is, the base 18 of the transistor 13 is connected to the fixed contact 19 of this single-pole, double-throw switch 22. When the grounded movable contact 20 of this switch is closed on contact 19 to indicate a day condition, base 18 is grounded, transistor 13 does not conduct, flip-flop 11 is considered to be in a set condition, and the collector of transistor 13 is relatively positive. Under the day condition, resetting of the flip-flop 11 is inhibited.

Opening of the switch 22 by moving selective contact 20 over into contact with fixed contact 21, the position into which this contact is placed during the night condition does not automatically reset flip-flop 11. The resetting of that flip flop is subject to a number of contingencies. The first of these is that switch 22 must be set for the night condition, removing the ground from base 18. The second condition is that there appears a positive voltage on line 23. That is, the connection to line 23 and the condition of the sensors at 10 must be such as to establish a positive voltage on line 23. In other words, the condition of line23 must be such as to indicate a safe condition. The sensors operate in such manner that when the sensors are in safe condition the voltage on line 23 is positive. When an alarm condition exists, then that voltage is zero. Reiterating, resetting of flip flop 22 is subject to the aforesaid second condition, i.e., that the sensors furnish a safe indication on line 23. The resetting of flip-flop 11 is subject to a third condition, ie., that the close switch 24 be closed.

When line 23 is encircuited with the base 18 of transistor 13, that base goes positive and transistor 13 conducts and transistor 12 ceases to conduct. This positive bias is provided from line 23, via the close switch 24, a resistor 25 and a diode 26, poled with its cathode adjacent base 18.

When the control flipflop 11 is in a set condition it inhibits the alarm circuit by cutting off transistor 33 and it activates a circuit that sends a day condition signal on line 29 to a transponder. The day-night indicating circuit comprises an NPN transistor 27 connected in the grounded emitter configuration with its base coupled by a series resistor 28 to the collector of transistor 13 and its collector providing an output on line 29. When the control flip-flop is in a set state the base of transistor 27 is positive and it conducts, furnishing a signal that indicates a day condition.

Assuming that contact 30 is connected to contact 35, then the combination of resistor 28 and transistor 27 is paralleled by a combination of resistor 31 and NPN transistor 32 so that transistor 32 conducts when flipflop 11 is in the set state and transistor 32 inhibits an alarm signal on transistor 33 because it causes the base of transistor 33 to move toward zero volts.

Neglecting for the moment the delay circuitry presently to be described, it will be seen from the foregoing that the collector of control flip-flop transistor 13 is directly connected to a contact 30 of a switch which comprises fixed contacts 30 and 34 and a movable contact 35. The present discussion is on the footing that contacts 30 and 35 are made. Contact 35 is connected via resistor 31 to the base of NPN transistor 32, which is arranged in the grounded emitter configuration with its collector coupled to the base of an NPN transistor 33, also connected in the grounded emitter configuration. Transistor 33 provides a collector output on line 36. The function of transistor 33 is to become conductive, in response to a zero voltage on line 23, in order to be able to send out on output line 36 an alarm indication, conveying intelligence that the condition of the sensors is that for an alarm.

From the description so far it will be seen that the functions of flip-flop 11, when in a set condition, are to cause to be sent out on line 29 a day signal and also to cause transistor 33 to be inhibited, so that it cannot convey an alarm signal.

Assuming connection of contacts 30 and 35, a resetting of flip-flop 11 removes the drive voltage from transistor 32 and therefore removes the inhibition from transistor 33.

It is sometimes desired to maintain the inhibition on transistor 33, even after a sensor is temporarily in an alarm condition. For example, assume that a customer opens the door of his house to depart the causes line 23 to go to volts. This would normally cause an alarm signal to appear on line 36. However, under such an assumption it is desirable that the alarm signal not appear.

The desirable result just stated is achieved by the pro vision of a flip-flop comprising NPN transistors 38 and 39. Bear in mind that the setting of the customers night switch, his departure through the door, and then the closing of the door cause the following sequence of events on line 23: first, a transition from a positive voltage to zero, as the door opens; second, a transition from zero to a positive voltage as the door closes. Transistor 40 inverts its input signal so that opening of the door causes its collector to go in the positive direction. The collector of transistor 40 is capacitively coupled by capacitor 41 to the base of NPN transistor 38 which is so arranged as to be conductive under the conditions which exist when switch 24 is closed. Transistor 38 remains conductive in response to the positive pulse from transistor 40 which occurs at the time that the door is opened. However, when the door closes the output of transistor 40 is a negative-going pulse which trips off transistor 38 so that transistor 39 becomes conductive. A negative pulse goes to transistor 32, via contacts 34 and 35, shutting transistor 32 off and removing the inhibition on transistor 33.

NPN transistors 38, 39 have their emitters grounded. The collector of each is connected to the base of the other, as by resistors 42 and 43. The collectors are connected to appropriate current sources (not shown) as by resistors 44 and 45. The immediately preceding discussion assumed that at the start, transistor 38 was conducting. Transistor 38 is always conducting when transistor 13 is not conducting, as when switch 22 is in the day condition or, even if switch 22 is in the night condition, provided that flip-flop 11 has not been reset. The reason for this is a resistive connection 46 between the collector of resistor 13 and the base of transistor 38. When transistor 38 conducts transistor 32 also conducts, inhibiting an output on line 36. It follows from the foregoing that whether contact 35 touches contact 30 or contact 34 the off condition of transistor 13 inhibits an alarm output on line 36.

Reference is now made to the alarm and safe signal channel which comprises sensors 10, line 23, resistor 47 and NPN transistors 40 and 33, cascaded, each with grounded emitter. The collector of transistor 40 is connected via resistance 48 to a suitable source of bias current (not shown) and that collector is coupled as by series resistor 49 to the base of transistor 33, the collector of which is connected to the safe-alarm output line 36.

It has been shown that when transistor 13 is in the off condition it inhibits night and alarm signal outputs on lines 29 and 36, respectively. When transistor 12 is in the off condition it places in a conductive state the NPN transistor 50, the collector of 12 being connected to the base of transistor 50 by resistance 51.

A pair of lamp circuits is connected between a suitable source of current (not shown) and the collector of transistor 50. One of these lamp circuits comprises a lamp 52, the collector-emitter circuit of transistor 53, and the collector-emitter circuit of transistor 50. The other lamp circuit comprises lamp 54, the collectoremitter circuit of transistor 55, and the collectoremitter circuit of transistor 50.

In response to the closing of switch 24, a positive voltage is applied via resistor 56 to the base of transistor 53, and, if transistor 12 is off, then lamp 52 goes on. In order to illuminate lamp 52 the following conditions must be satisfied: a safe indication on line 23; switch 22 in the night condition; the switch 24 must have been closed to reset flip-flop 11. When transistor 12 is conducting the operation of the close verification lamp 52 is inhibited. A test of similar nature can be made by a ring back signal from a remote location, applied via resistor 57 to the base of transistor 55, illuminating lamp 54 under the condition that transistor 50 is conducting. The lamp circuit for lamp 54 is also inhibited when transistor 12 is conductive.

Reiterating, the cycle of operation is as now described. When switch 22 is in the day position the baseemitter circuit of transistor 13 is short-circuited so that transistor 27 conducts, indicating a day condition on line 29. Additionally, transistor 32 conducts, inhibiting any alarm output on the alarm line 36. Transistor 12 is conducting, inhibiting the operation of the circuits for lamps 52 and 54.

If the switch 22 is moved to the night position, the short-circuit is removed from the base-emitter circuit of transistor 13. Pushing the close switch 24 will reset flip-flop 11 only if a safe condition is indicated on line 23. Assuming a safe condition and the closing of switch 24, transistor 13 conducts. Transistor 27 goes off, indicating the night condition on line 29. Transistor 32 goes off and that permits base drive to transistor 33 if an alarm condition should occur. In such event an alarm signal would appear on line 36. The off condition of transistor 12 puts transistor 50 in a conductive state so that, when button 24 is pressed, the illumination of lamp 52 verifies that switch 22 is in a night condition and the sensing devices are in a safe condition.

Thus the invention provides, in an alarm system of the type which includes an alarm-transmitting channel 47, 40, 49, 33, 36, a subsystem for rendering the operation of that channel dependent on a plurality of environmental conditions comprising a safe state of the sensors (as indicated on 23) and recognition of the night season (by opening 22) and a sensor-sampling order (by closing 24) comprising: means 11, 37, 31, 32 including a flip-flop 11 for enabling or inhibiting said channel, said flip-flop being normally in the set state in which it inhibits said channel, command means 22 for inhibiting a change of state of the flip-flop under day conditions and permitting such change of state under night conditions, and means 24 for sampling the output of the sensors and causing said flip-flop 11 to change state if the night command has been rendered and if the output of the sensors indicates a safe condition.

1 also provide means 52, 53 for verifying said change of state has occurred, and means 50 responsive to said change of state for enabling the verifying means, the

verifying means being coupled to the sampling means by 56.

The signal channel enabling-inhibiting means 11, 37, 31, 32 includes means 32 for short-circuiting the signal channel and a second flip-flop 38, 39 controlled by the signal channel, via 41, and means 37 for selectively coupling the short-circuiting means either to the sec ond flip-flop or to the first flip-flop so as to permit removal of the short-circuit either with a delay or immediately, as desired.

While there has been shown and described what is at present believed to be the preferred embodiment of the invention, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined in the appended claims.

Having described my invention, I claim:

1. In a burgular and/or fire alarm system of the type including at least one sensor, having safe and alarm states and an alarm signal channel adapted to intercouple said sensor to a monitor, the combination of:

means, including a binary control device adapted normally to assume one of two states, for disabling said channel,

means, including a circuit closure, responsive to a safe state of said sensor for changing the state of said binary device, and

day-night switching means, responsive to an operators command, for selectively inhibiting or enabling said change of state.

2. In an alarm system the combination of:

sensor means for sensing safe or alarm conditions,

means having a signal channel for transmitting signals of an alarm condition,

a first binary device adapted normally to assume a set state,

switch means for applying the output of the sensor means to said first binary device,

command means adapted to respond to the command of an operator to inhibit or enable a change of state of said first binary device,

means coupled to said first binary device for convey ing intelligence as to whether the command means is inhibiting or enabling a change of state of the first binary device,

means for inhibiting the output of said signal channel,

a second binary device,

means for selectively coupling the inhibiting means to the output of either the first binary device or the output of the second binary deivce so that the inhibiting means may be disabled in response to a change of state of either the first device or the second binary device, the second binary device being intercoupled to a point in the signal channel and so proportioned and arranged that it does not change state in response to a first alarm condition but does change state in response to an immediately following safe condition, and

means enabled, when the first binary device resets, in

response to closing of said switch means and a safe condition, to verify the existence of a reset state of said first binary device, said reset state being subject to the fulfillment of all of three contingencies: first, the existence of a safe condition at the output of the sensor means, second the closing of the switch means, and third, the issuance of an en abling command by the command means.

3. In an alarm system of the type which includes an alarm-transmitting channel and a plurality of sensors, a subsystem for rendering the operation of that channel dependent on a plurality of environmental conditions comprising a safe state of the sensors and recognition of the night season and a sensor-sampling order comprising:

means including a flip-flop for enabling or inhibiting said channel, said flip-flop being normally in the state in which it inhibits said channel, command means for issuing day commands and night commands and inhibiting a change of state of the flip-flop under day conditions and permitting such change of state under night conditions, and

means for sampling the output of the sensors and causing said flip-flop to change state if the night command has been rendered and if the output of the sensors indicate a safe condition.

4. The combination in accordance with claim 3, plus means for verifying that said change of state has occurred, and means responsive to said change of state for enabling the verifying means, the verifying means being coupled to the sampling means. 5. The combination in accordance with claim 4, in which the signal channel enabling-inhibiting means includes means for short-circuiting; the signal channel 

1. In a burgular and/or fire alarm system of the type including at least one sensor, having safe and alarm states and an alarm signal channel adapted to intercouple said sensor to a monitor, the combination of: means, including a binary control device adapted normally to assume one of two states, for disabling said channel, means, including a circuit closure, responsive to a safe state of said sensOr for changing the state of said binary device, and day-night switching means, responsive to an operator''s command, for selectively inhibiting or enabling said change of state.
 2. In an alarm system the combination of: sensor means for sensing safe or alarm conditions, means having a signal channel for transmitting signals of an alarm condition, a first binary device adapted normally to assume a set state, switch means for applying the output of the sensor means to said first binary device, command means adapted to respond to the command of an operator to inhibit or enable a change of state of said first binary device, means coupled to said first binary device for conveying intelligence as to whether the command means is inhibiting or enabling a change of state of the first binary device, means for inhibiting the output of said signal channel, a second binary device, means for selectively coupling the inhibiting means to the output of either the first binary device or the output of the second binary deivce so that the inhibiting means may be disabled in response to a change of state of either the first device or the second binary device, the second binary device being intercoupled to a point in the signal channel and so proportioned and arranged that it does not change state in response to a first alarm condition but does change state in response to an immediately following safe condition, and means enabled, when the first binary device resets, in response to closing of said switch means and a safe condition, to verify the existence of a reset state of said first binary device, said reset state being subject to the fulfillment of all of three contingencies: first, the existence of a safe condition at the output of the sensor means, second the closing of the switch means, and third, the issuance of an enabling command by the command means.
 3. In an alarm system of the type which includes an alarm-transmitting channel and a plurality of sensors, a subsystem for rendering the operation of that channel dependent on a plurality of environmental conditions comprising a safe state of the sensors and recognition of the night season and a sensor-sampling order comprising: means including a flip-flop for enabling or inhibiting said channel, said flip-flop being normally in the state in which it inhibits said channel, command means for issuing day commands and night commands and inhibiting a change of state of the flip-flop under day conditions and permitting such change of state under night conditions, and means for sampling the output of the sensors and causing said flip-flop to change state if the night command has been rendered and if the output of the sensors indicate a safe condition.
 4. The combination in accordance with claim 3, plus means for verifying that said change of state has occurred, and means responsive to said change of state for enabling the verifying means, the verifying means being coupled to the sampling means.
 5. The combination in accordance with claim 4, in which the signal channel enabling-inhibiting means includes means for short-circuiting the signal channel and a second flip-flop controlled by the signal channel, and means for selectively coupling the short-circuiting means either to the second flip-flop or to the first flip-flop so as to permit removal of the short-circuit. 